The present invention relates to a method of feeding portions of wrapping material on a cigarette packing machine.
In particular, the present invention relates to a method of feeding, on a cigarette packing machine, portions of wrapping material from which to form the inner wrapping of respective packets of cigarettes.
On cigarette packing machines, groups of cigarettes, each normally comprising twenty cigarettes arranged in three layers, are formed inside respective pockets of a conveyor, and are normally fed successively to a rotary head normally presenting a number of seats, each designed to receive a respective group of cigarettes. Once inside said seat, each group is fed, by rotating the head through a given angle about its axis, to a folding station, which is also fed successively with portions of wrapping material. At the folding station, each group of cigarettes is normally pushed radially out of the seat and against a respective portion of wrapping material, and is fed, together with the wrapping material, into an outer radial pocket on a wrapping wheel, so that the wrapping material is folded in a U about the respective group of cigarettes as this is inserted inside the pocket on the wrapping wheel.
According to U.S. Pat. No. 4,918,901, said portions of wrapping material are made of foil, and are fed to the folding station along a guide with an end stop element on which the foil portions are arrested successively just before receiving the respective groups of cigarettes. That is, on being cut transversely at a given rate off a continuous strip, the foil portions are engaged at the front end by suction elements on the rotary head, and are fed along the guide until they are arrested on the stop element in a substantially vertical folding position suitable for receiving the respective groups of cigarettes.
The above known feed device has been found to operate excellently when dealing with portions of material with a high degree of rigidity, such as foil, but is substantially unsuitable for feeding portions of substantially nonrigid material, such as the biodegradable materials recently employed in place of foil, which tend to curl if not controlled constantly along the whole length of the portion as they are fed to the folding station.